1. Field of the Invention
The present invention relates to an image projection apparatus and a movable body.
2. Description of the Related Art
An image projection apparatus that forms an intermediate image on an intermediate image forming member from light emitted by a light source device, causes the intermediate image light to pass through a plural-film optical member where a plurality of optical films are laminated to obtain a projected image, and projects the projected image, is known.
For example, Japanese Unexamined Patent Application Publication No. 2016-197173 (Patent document 1) discloses a head-up display (HUD) (an image projection apparatus) including a liquid-crystal panel (an intermediate image forming member) forming an intermediate image from light emitted by a light source device; and a cold mirror (a plural-film optical member) reflecting image light exiting the liquid-crystal panel toward the windshield of a vehicle. The HUD further includes a phase shifter such as a phase difference film on the optical path between the liquid-crystal panel and the cold mirror to convert image light to be incident on the cold mirror into an s-wave (i.e., image light that is s-polarized light upon being reflected by the cold mirror).
Thereby, according to a theory, an incidence of a p-wave (i.e., image light that is p-polarized light upon being reflected by the cold mirror) onto the cold mirror is suppressed, and as a result, it is possible to suppress a change on a per-wavelength basis of the polarization state of light exiting the cold mirror occurring due to the phase difference between the polarized light components of an the s-wave and the p-wave incident on the cold mirror. Thus, according to the theory, it is possible to cause a user to see a projected image having colors close to the colors in the intermediate image.
Note that an expression such as “image light that is p-polarized light upon being reflected by the cold mirror” will be referred to by an expression such as “p-polarized light with respect to reflection by the cold mirror”. In the same way, an expression such as “image light that is s-polarized light upon being reflected by the cold mirror” will be referred to by an expression such as “s-polarized light with respect to reflection by the cold mirror”.